This invention relates to a method and apparatus for adjusting contrast based on heating and cooling rates. More specifically, this invention relates to adjusting the contrast level of a data display module in an appliance.
Appliances such as dishwashing machines, clothes washing machines, clothes drying machines, electric ranges, as well as other appliances may now contain data display modules such as LCD panels. In these types of appliances, there are problems with the use of LCD panels or other display modules. The problem relates to the temperature of the data display module. As the appliance heats up the data display module fades due to the temperature increase. The fading of the data display module obscures the display from the user of the appliance or otherwise makes the display difficult to read.
If the data display module allows for user adjustment of the contrast level of the data display module, then a user can adjust the contrast to compensate for the fading of the LCD when the appliance heats up. Eventually, however, after the appliance is turned off or otherwise begins to cool, the user will have to adjust the contrast level to compensate for the prior adjustment made.
Various methods of automatically or electronically adjusting data display modules have previously been used. One such method is to use a temperature sensor to measure the temperature of a data display module and then alter the contrast level based on the temperature sensed at the LCD device. This has been accomplished through use of a feedback circuit or through application of a mathematical relationship between the temperature-measured and a voltage or a frequency to be applied to a liquid crystal display. One problem with this methodology is that a temperature sensor is required. This adds to the cost of manufacturing and may affect the reliability of the device.
Thus, it is a primary object of the present invention to provide a method and apparatus for control of the contrast level of the data display module in an appliance which improves upon the state of the art.
Another object of the present invention is to provide an apparatus and method for compensating for temperature changes in a data display module which does not require a temperature sensor.
Yet another object of the present invention is to provide a method and apparatus of adjusting the contrast level of a data display module in an appliance that does not significantly add to the cost of the manufacturing the appliance.
A further object of the present invention is to provide a method and apparatus for adjusting the contrast level of the data display module in an appliance that may be implemented in software.
A still further object of the present invention is to provide an apparatus and method for adjusting a contrast level of a data display module in an appliance that can take into account operator adjustments of the contrast level.
These and other objects, features, or advantages of the present invention will become apparent from the Specification and claims.
The present invention is a method and apparatus for automatically adjusting the contrast level of a data display module in an appliance. The apparatus of the invention provides for an appliance having an intelligent control electrically connected to the appliance and adapted for controlling the appliance, a data display module capable of contrast adjustment electrically connected to the intelligent control, and a data storage medium electrically connected to the intelligent control storing software instructions for monitoring the amount of time the appliance is in an active state, and instructions for compensating for the temperature change associated with the amount of time by adjusting the contrast level of the data display module.
The invention determines whether the appliance is in an active state, and then estimates the temperature change in the data display module that is to be compensated for based upon the amount of time the appliance has been in the active state. The invention then adjusts the contrast level to the data display module to compensate for the temperature change in the data display module.
Another aspect of the invention is to compensate for the condition that occurs when the appliance enters the active state prior to being fully cooled. A further aspect of the present invention is to compensate for any user adjustment of the contrast level. Thus the present invention provides for the advantages of not requiring a temperature sensor to compensate for temperature changes in a data display and module. This allows for automatic contrast adjustment of a data display module without requiring increased manufacturing costs.